KT77 FTW

I use a Grant lumley desgn point to point wired ST70 reference Stereo Power Amp currently I'm using Gold Lion Quad KT88; 2x RCA JAN NOS ECC83 & 2x Gold Lion ECC82.

In this design ECC82 (12AU7) tubes are used as a preamplifier or driver tubs. They are a lower gain compared to the ECC83, making it suitable for applications where a moderate amplification factor is needed.
The 2x ECC83 (12AX7) tubes are used as a high-gain preamplifier tubes providing the a higher amplification factor, making it ideal for initial signal amplification

In the Lumley ST70, these tubes are used in the input and phase splitter stages to ensure proper signal amplification and phase splitting before driving the output tubes.

I can use this amp easily in ultra linear and Triode mode by simply switching them when placng the amp in stand by mode briefly.

Ultimately it depends on my mood and our source material as to my preference but very simply put the amp sounds more incisive and dynamic in ultra linear and just a bit sweeter and holographic in triode mode.

I have completely recapped the amp using Mundorf Mcap Supreme Silver Gold OIL 1200VDC film capacitors for coupling along with top end Nichicon and Audionote elsewhere. Topping off with massive Nichicon reservoirs/ Filter caps. The amp has huge hand wound inputvand output transformers and can now be set to output into 4 ohms or 8 ohms via Rhodium binding posts.

I will never sell it its such a thing of beauty and sounds as good as it looks. I think fir me as long as the KT88's are as good quality as I can afford the major sound changes come via sourcing top quality ECC82  & ECC83 and experimenting although I am so satisfied with how this ampmperforms hooked up to a Tim De Pavaracini designed all tube EAR 912 pre. I just dont feel the need to tinker, its powerful enough to drive my Proac Carbon Pro speakers down low with ease its very holographic and sounds dynamic even at late night listening levels.

I love my tube based system but I don't dicriminate on source I have a much modified LP12  decent digital source streamer about to be made even better by a Chord TT2 & M Scaler a vintage Sony CD player & Tube based CD player too. I'm  not too much of an Audiophile niw that I am listening to music much more than the system. It must beca sign that I'm close to where I want to be gear wise. I just cant see me being without valves in my system.

I would say PP amp do sound great. It really depending on the design to get the very best out from it. The most common problem of the manufacturers are trying to get maximum power from the amp; more the better. However, it pushes the power tubes working in the non-linear Class AB region. Even though the THD figure looks good, it doesn't sound right at all. 

My friend built a PP amp with 807 and I built one with KT66, EL34, or 6A3. The output power is less than 8 watts because we set the B+ to around 320Vdc and idle current of the power tube at 60mA. Also, both driver and power stages are using CCS at the common cathode to form the full differential/balance stages. 

We are so surprised how good our amps sounds that surpassed the single ended amps that we ever built.

Johnny

I noticed that both KT150 and KT170 are very linear in triode mode like the 300B and 845 DHT tubes. 

I expect they are the excellent performance if they can be used in small/medium power class A environment. 

it's purely a matter of design

@inna That's the answer.

If you want to hear a really musical KT88 based amp, the Harmon Kardon Citation 2 (properly refurbished) is a good place to start.

It makes a difference too if the amp is pentode or Ultra-Linear and also what class of operation its set up for. You can't get away from the simple fact that the larger the output transformer is, the more critical it becomes and the harder for it to make bandwidth. IMO this latter issue might be the most important.